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Moon Dial Clock

Gina

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This clock runs off a stepper motor controlled by Arduino and Real time Clock module.  It is about 300mm square with analogue display of hours and minutes with a sweep seconds hand.  Atop the main clock face is a globe displaying the phase of the moon.  The clock face is of clear acrylic to show all the gears etc.  This clock is finished and has been running for several months.



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This sounds like an interesting project and I too would like to see an image of what you have in mind. I have seen some digital display types but this sounds more 'analogue' (albeit with digital controller) and that sounds much more appealing.

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Gina

Posted (edited)

As requested, a photo of the finished clock.  I'll be adding details of the construction shortly, copying relevant excerpts from my rather long thread in the DIY Astronomer forum.  It's not really a blue moon, it's lit with a white LED but the digital photo has coloured it blue :D

Clock Final 01.jpg

Edited by Gina
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I'll try and pick the bones out of a very long thread about making this clock to post here.  Just the final version, because there were several "blind alleys".  Now to find the original thread...

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Gina

Posted (edited)

Oops, this Blog wants more... All the works with lots of pictures.  Found it!!  HERE.  It's pretty big - 46 pages.

Edited by Gina

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I've come here because after several years of perfect operation and timekeeping this clock has developed a fault following a power cut during the night a few days ago.  The Hall sensor that detects the position of the minute hand has become unreliable. 

After a power cut or operation of the GMT/BST switch, the clock is run very fast until the hour hand is detected just before the 12 o'clock position with the minute hand at about ten to the hour.  At this point the clock slows down allowing time for the minutes Hall sensor to detect the minute hand at the 12 o'clock position.  The 12 o'clock position having been found the amount of rotation required to get to the right time is calculated from the time given by the Real Time Clock module.  The clock is driven fast until the calculated position is reached and then run at normal rate.  The result is that the clock shows the correct time to within a few seconds.

I now need to find out why the minutes Hall sensor is not detecting the minute hand or possibly using another method of detecting when the minute hand is at exactly 12 o'clock.

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Managed to move the hands nearer the clockface and hence the tiny magnets in the ends nearer the Hall sensors and get the clock working but I think there is a future project here to fix the problem properly to provide more reliability.

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Drat changing the clocks - it's upset my Moon Dial Clock.  I have a switch on the top which determines GMT or BST and when operated restarts the clock as well as determining whether to add an hour for BST.  Flipped it this morning for the clock change and the hands sensors are not working.  Have to switch it off and make sure the hands are as close to the face as possible.  As I said above, this could do with a design change to make it more reliable.

The position of the hands is detected by small magnets in the ends of the hands and Hall devices built into the clock face.  I was thinking the minutes shaft went through to the back of the clock but it doesn't - its the seconds shaft - the minutes is a sleeve like the hours but longer.  The sleeves only go back as far as the relevant wheel/gear.  All this seemed a good idea at the time and avoids the standard clock slipping clutch which is the standard way of setting the time and seemed difficult to implement in a plastic geared clock.  Also, the ability to set the time automatically was a nice extra.

I really don't want to completely redesign and rebuild this clock.  Maybe see if I can use bigger magnets.

Edited by Gina

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